This study investigates the impacts of infrastructure policy on the dynamic coordination between urban development and ecological sustainability in China. We construct an urban–environment composite system synergy degree using a coupling coordination model. To identify causal effects, we apply a continuous treatment difference-in-differences design to panel data from 31 provinces, evaluating the implementation strength of electric vehicle (EV) charging infrastructure development guidelines (2015–2020). Our findings reveal two key insights. First, there exists a structural asymmetry in policy effectiveness: while ecological conditions improve significantly, the urban subsystem, however, exhibits a slower and more delayed coordination response, leading to a statistically significant but unbalanced enhancement in overall system synergy. Second, we observe notable spatial heterogeneity, with the Central region experiencing the most pronounced coordination gains, whereas the Western region exhibits weaker responses to policy implementation. This research advances the theory of sustainable urban development by highlighting the critical roles of policy intensity, subsystem imbalance, and regional diversity. It offers actionable evidence for tailoring EV infrastructure strategies to the differentiated needs of regional development contexts.
Sheng et al. (Sun,) studied this question.